National Geographic photographer Joel Sartore is on a mission to photograph every species in zoos and aquariums — and help save them in the process.

To say that National Geographic photographer Joel Sartore has his hands full is an understatement: He’s in the process of photographing every single animal species in zoos and aquariums.

When he’s between the photoshoots that send him everywhere from the Galapagos Islands to Antarctica, Sartore spends his time at zoos and aquariums photographing animals for his personal venture, The Biodiversity Project. This huge undertaking was Sartore’s idea, and of the 6,000 species he estimates are in zoos and aquariums, he’s already captured nearly a third.

"The goal of this project is to get people to look these things in the eye before they go extinct," he said in a recent interview with NPR. "Not everything I shoot is rare, but a lot is. I just figure, for a lot of these species, these pictures are all that's going to remain.”

Sartore may sound fatalistic and that’s because he is. He’s known for his book “Rare: Portraits of America’s Endangered Species” and most of his stories in National Geographic have focused on those animals whose numbers are declining, but in his mind, every single animal — whether it’s listed as endangered or not — is in danger.

“All these animals are ambassadors. They serve to remind us of what we had or what we have, hopefully, and that it's amazing," he told NPR.

Sartore inches his way toward a juvenile caiman in Bolivia's Madidi National Park.

What first inspired Sartore’s interest in these animals? He says it was his mother’s Time-Life picture book called “The Birds,” which included photos of several extinct bird species. As he flipped through the pages of animals, he knew no one would ever see again, he came across a photo of the very last passenger pigeon, a bird named Martha that was kept at the Cincinnati Zoo until she died in 1914, and he was astounded.

“This was once the most numerous bird on Earth, with an estimated population of 5 billion, and here it was reduced to this single female, with no hope of saving it. I couldn’t understand how anyone could tolerate this. I still feel the same way, and I work hard to prevent this from ever happening again.”

Sartore hopes that by creating a catalog of the planet’s species, people will look these animals in the eye and join him in his crusade to save them. As he says, “Photography can do a huge service in two ways. It can expose environmental problems as nothing else, and it can help get people to care.”

Check out some of Sartore's amazing photos from The Biodiversity Project below, and visit his website to see more of his compelling pictures.